Process of producing hydrocyanic acid



Patented Mar. 20,

UNlTED STATES PATENT OFFICE PROCESS OF PRODUCING HYDROCYANIC ACID Eduard Miinch and Fritz Nicolai, Ludwigshafenon-the-Rhine, Germany, assignors to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on- V the-Main, Germany, a corporation of Germany No Drawing. Application March 31, 1927, Serial No. 180,057. In Germany April 10, 1926 10 Claims, (01. 23-151) i We have found that in the catalytic production of hydrocyanic acid from formamide, or formamide containing ammonium formate, very good yields of hydrocyanic acid may be obtained 5. by passing the vapors of formamide or formamide containing ammonium forinate in a highly diluted condition and at high velocity, in the presence of metals but in the absence of catalysts capable of splitting 01f water.

v For the said purpose those metals are suitable, the catalytic action of which is not unfavorably influenced by the high temperature employed in the process and by the action of formamide and the reaction products, and which are not molten mat the reaction temperature. For example iron,

nickel aluminium and copper and alloys containing one or more of these metals are very suitable. The metals may be employed in any convenient form such as granules, turnings, Wire 2 netting, with or Without carriers, or in conjunction with other compounds which are not dehydrating catalysts. It is even suflicient to make the walls of the reaction vessel of the desired metal, or to line them with it. The reaction vessel preferably consists of a tube, the cross section and length of which are adapted to the conditions needed for the rapid passage of the vapors.

In order to obtain strong dilution and high velocity, it is necessary to pass the vapors of formamide, or formamide containing ammonium formate, over the metal or through the metal tubes either under reduced pressure or in admixture with ammonia or inert gases containing the same, or with inert gases alone.

The temperatures needed to give the best yield vary with the kind of metal employed. For example, Whereas temperatures between about 350 and 450 C. are advisable in the case of mild steel 40 ,or VZA steel (of the firm of Krupp), which is a chromium-nickel-steel containing '72 per cent of iron, 20 to 21 per cent of chromium and 6 to 7 per cent of nickel besides small amounts of copper, manganese, carbon, silicon and phos- 51'Lphorus, a temperature of from 450 to 500 C. is suitable when nickel is used and a temperature of from 500 to 600 C. in the case of aluminium. The temperatures suitable are also dependent on the form in which the metal is used. Temperatures as low as 300 C. may be employed in the reaction, since considerable yields are obtained even at that temperature, and temperatures as high as 700 C. give good yields.

The following examples will further illustrate how the said invention may be carried into practical effect but the invention is not limited to these examples.

Example 1 The vapors of formamide are passed through an iron coiLabout 3 metres long, 8 millimetres inside diameter, and heated to 370 C., undera reduced pressure equivalent to from 1 0 to 20 mil limetres of mercury and at such velocity that about 1 to 2 molsof formamide are passed through per hour. A yield of 93 per cent of the theoretical amount of hydrocyanic acid is obtained.

If the iron coil be replaced by one of aluminium or nickel of similar dimensions, and the tempera-' ture be maintained at from 500 to 550 C. in the former case and at from 480 to 500 C. in the latter, a yield of over per cent of hydrocyanic acid is also obtained.

Example 2 Example 3 The vapors of formamide are passed, at the rate of 2 to 5 mols per hour and under a diminished pressure equivalent to about 10 millimetres of mercury, through a V2A steel tube, 120 centimetres long and 25 to 30 millimetres inside diameter, heated to from 420 to 450 C. and. the issuing vapors are passed into caustic soda solution. The yield of hydrocyanic acid in the form of sodium cyanide, amounts to over 90 per cent of the theoretical.

Example 4 If the V2A steel tube mentioned in Example 3 be filled to about two-thirds with iron turnings, the amount of formamide passed through may be nearly doubled without impairing the yield.

Example 5 .11

If the iron turnings mentioned in Example 4 be replaced by aluminium shreds, contained, for example, in a heating tube of quartz, about per cent of the formamide will be converted into hydrocyanic acid at from 570 to 580 C.

'I'urnings or granules oi. other metals, such as manganese, or alloys such as ferro-silicon', with or without carriers, or in conjunction with other compounds, may be employed in a similar man- 5 ner. j

We claim:

1. In the production of hydrocyanic acidby exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing formamide vapors in ahighly diluted condition and at a high speed in contact with a solid metal, the catalytic action of which is'not unfavorably influenced by thehigh temperature and by formamide and the reaction products, said vapors attaining the reaction temperature only when in contact with said metal.

2. In the production of hydrocyanic acid by exposing formamide vapors to the action of a tem-.

perature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of pass- 'ing 'formamide vapors together with ammonium formate in a highly diluted condition and at a high speed in contact with a solid metal, the

catalytic action of which is not unfavorably infiuenced by the high temperature and by formamide and the reaction products, said vapors attaining the reaction temperature only when in contact'with said metal.

3.'In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300" and 600 C. in the absence of dehydrating catalysts, the step of passing formamide vapors in a highly diluted con- 3,,;dition and at a' high speed through a narrow reaction space, the inner surface of which comprises a solid metal, the catalytic action of which is not unfavorably influenced by the high temperature and by formamide and the reaction 40; -.products, said vapors attaining the reaction temperature only when in contact with saidmetal.

4. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of 'passing formamide vapors under reduced pressure in contact with a solid metal, the catalytic action of which is not unfavorably influenced by the high temperature and by formamide and 0 the reaction products, said vapors attaining the reaction temperature only when in contact with said metal.

5. In the production of hydrocyanic acid by exposing formamide vapors to the action of a ';temperature between about 300 and 600 C. in

the absence of dehydrating catalysts, the step of passing formamide vapors strongly diluted'by a gas not interfering with the desired reaction and at a high speed in contact with a solid metal, the catalytic action of which is not unfavorably influenced by the high temperature and by formamide and the reaction products, said vapors attainingthe reaction temperature only when in contact with said metal.

6. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing formamide vapors in a highly diluted condition and at a high speed in contact with a metal comprising iron, said vapors attaining the reaction temperature only when in contact with said metal.

7. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing formamide vapors together with ammonium formate in a highly diluted condition and at a high speed in contact with a metal comprising iron, said vapors attaining the reaction temperature only when in contact with said metal.

8. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing formamide vapors in a highly diluted condition and at a high speed through a narrow reaction space, the inner surface of which comprises a metal comprising iron, said vapors attaining the reaction temperature only when in contact with said metal.

9. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing formamicle vapors under reduced pres-- sure in contact with a metal comprising iron, said vapors attaining the reaction temperature only when in contact with said metal.

10. In the production of hydrocyanic acid by exposing formamide vapors to the action of a temperature between about 300 and 600 C. in the absence of dehydrating catalysts, the step of passing rormamide vapors strongly diluted by a gas not interfering with the desired reaction and at a high speed in contact with a metal comprising iron, said vapors attaining the reaction temperature only when in contact with said metal.

EDUARD MiiNcH. FRITZ NICOLAI.

i I f I 7 9. 

